1. Field of the Invention
The present invention relates to a collimator lens, an illumination device including the collimator lens, and a microscope including the illumination device, and more particularly, to a collimator lens configured with a single lens, an illumination device including the collimator lens, and a microscope including the illumination device.
2. Description of the Related Art
In a fluorescent observation using a microscope, an illumination device including a xenon light source, a high-pressure mercury light source or the like, by which a high output can be obtained, has been widely used to excite a fluorescent substance heretofore. With a xenon light source or a high-pressure mercury light source, a radiated amount of heat is very large although a high output can be obtained. Accordingly, an optical system included in a conventional illumination device is normally designed so that a focal length is increased by a glass lens having high heat resistance.
In recent years, the need for a light source including a solid-state light emitting element having features such as less heat generation, compactness and a long life has been increasing, and, for example, an illumination device using a light source including a solid-state light emitting element as disclosed by Japanese Laid-open Patent Publication No. 2005-208571 has been developed.
The illumination device disclosed by Japanese Laid-open Patent Publication No. 2005-208571 includes a light source having an LED, which is a solid-state light emitting element, and a collimator optical system for guiding illumination light of a light distribution specific to an LED in a specified direction with high illumination efficiency.
For an illumination device used for a fluorescent observation, an excitation intensity demanded to excite a fluorescent substance needs to be secured. Accordingly, it is important for an optical system included in an illumination device, especially, an optical system of an illumination device including a solid-state light emitting element to implement a high transmittance and to irradiate light emitted from a light source efficiently on a specimen. Moreover, the illumination device including the solid-state light emitting element is expected to be more advantageous than a conventional illumination device in terms of cost.